Honeycomb filter

ABSTRACT

A honeycomb filter includes a pillar-shaped honeycomb substrate including a porous partition wall that defines a plurality of cells extending from an inflow end face to an outflow end face, an inflow side plugging portion disposed at the inflow end face of the honeycomb substrate to plug open ends of outflow cells; and an outflow side plugging portion disposed at the outflow end face of the honeycomb substrate to plug open ends of inflow cells other than the outflow cells. The honeycomb substrate includes the partition wall that defines two of the inflow cells by division. An average of the plugging length L OUT  of the outflow side plugging portions disposed in the inflow cells of the honeycomb substrate is larger than an average of the plugging length L IN  of the inflow side plugging portions disposed in the outflow cells of the honeycomb substrate.

present application is an application based on JP 2016-058272 filed onMar. 23, 2016 with Japan Patent Office, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to honeycomb filters. Specifically thepresent invention relates to a honeycomb filter having excellenttemperature-rising property and capable of increasing the depositionlimit of particulate matter, such as soot, during the regenerationoperation to burn the soot trapped with the filer for removal.

Description of the Related Art

Internal combustion engines are used as a power source in variousindustries. Exhaust gas emitted from an internal combustion engineduring fuel burning, however, contains particulate matters, such as sootand ash, together with toxic gas, such as nitrogen oxides. Hereinafterthe particulate matters may be called “PM”. “PM” stands for “ParticulateMatter”. Regulations on the removal of PM emitted from a diesel engineare becoming stricter worldwide. A honeycomb-structured wall flow typefilter, for example, has been used for a filter to remove such PM.

Various types of honeycomb filters have been proposed as the wall-flowtype filter, and such a filter includes a honeycomb substrate having aporous partition wall that defines a plurality of cells serving as athrough channel of fluid, and a plugging portion disposed at the openends of the plurality of cells on any one side (see, for example, PatentDocuments 1 to 4). Such a honeycomb filter has inflow cells having aplugging portion at their outflow end faces and outflow cells having aplugging portion at their inflow end faces, the inflow cells and theoutflow cells being disposed alternately via the partition wall. Theporous partition wall serves as a filter to remove PM.

For a long term use of a honeycomb filter, the honeycomb filter has tobe regenerated regularly. This is because PM, such as soot, is depositedinside of the honeycomb filter over time, so that the pressure loss ofthe filter increases gradually. In order to bring back the filteringperformance of the honeycomb filter closer to its initial state, PM,such as soot, deposited inside of the honeycomb filter has to be burnedwith a high-temperature gas for removal. For a smooth regenerationtreatment, a honeycomb filter may be loaded with catalyst to burn thesoot for removal. For such catalyst, noble metals, such as platinum andpalladium, are used. In the following, the operation to burn the sootdeposited inside of a honeycomb filter may be called simply“regeneration” or “regeneration operation” of the honeycomb filter.Particularly the operation to increase the temperature of exhaust gasflowing into a honeycomb filter regularly and intentionally for theregeneration may be called “forced regeneration”.

-   -   [Patent Document 1] JP-A-2007-209842    -   [Patent Document 2] JP-A-2012-081415    -   [Patent Document 3] JP-B-4279497    -   [Patent Document 4] JP-B-4567674

SUMMARY OF THE INVENTION

When a honeycomb filter as described in Patent Documents 1 and 2 isregenerated, the soot trapped in the honeycomb filter may be burned atone time. The soot trapped by the honeycomb filter may be carried awaywith the flow of exhaust gas gradually toward the outflow end face ofthe inflow cells. If the honeycomb filter in such a state isregenerated, the temperature of the honeycomb filter increases at theoutflow end face, especially at the outflow end face in the inflowcells. This may lead the problem that cracks are likely to occur in thehoneycomb filter. For instance, if a conventional honeycomb filter has asmall limit “amount of soot deposited” not causing cracks during forcedregeneration, and the intervals for the forced regeneration is long,cracks may occur in the honeycomb filter during forced regeneration.Hereinafter “the limit amount of soot deposited not causing cracksduring forced regeneration” may be called “a deposition limit” of thesoot.

In view of such problems of the conventional techniques, the presentinvention aims to provide a honeycomb filter having excellenttemperature-rising property and capable of increasing the depositionlimit of particulate matter, such as soot, during the regenerationoperation to burn the soot trapped with the filer for removal.

The present invention provides the following honeycomb filter.

According to a first aspect of the present invention, a honeycomb filteris provided including: a pillar-shaped honeycomb substrate including aporous partition wall that defines a plurality of cells extending froman inflow end face to an outflow end face; an inflow side pluggingportion disposed at the inflow end face of the honeycomb substrate toplug open ends of outflow cells that are a part of the plurality ofcells; and an outflow side plugging portion disposed at the outflow endface of the honeycomb substrate to plug open ends of inflow cells otherthan the outflow cells of the plurality of cells, wherein the honeycombsubstrate includes the partition wall that defines two of the inflowcells by division, and an average of plugging length L_(OUT) of theoutflow side plugging portions disposed in the inflow cells of thehoneycomb substrate is larger than an average of plugging length L_(IN)of the inflow side plugging portions disposed in the outflow cells ofthe honeycomb substrate.

According to a second aspect of the present invention, the honeycombfilter according to the first aspect is provided, wherein the average ofthe plugging length L_(OUT) is larger than the average of the plugginglength L_(IN) by at least 1.0 mm.

According to a third aspect of the present invention, the honeycombfilter according to the second aspect is provided, wherein the averageof the plugging length L_(OUT) is larger than the average of theplugging length L_(IN) by 1.0 to 4.0 mm.

According to a fourth aspect of the present invention, the honeycombfilter according to any one of the first to third aspects is provided,wherein plugging length L_(OUT) in the cell extending direction of theoutflow side plugging portion disposed in one inflow cell of the inflowcells is larger than plugging length L_(IN) in the cell extendingdirection of the inflow side plugging portion disposed in the outflowcell adjacent to the one inflow cell via the partition wall.

According to a fifth aspect of the present invention, the honeycombfilter according to the fourth aspect is provided, wherein the plugginglength L_(OUT) of the outflow side plugging portion disposed in the oneinflow cell is larger than the plugging length L_(IN) of the inflow sideplugging portion disposed in the outflow cell adjacent to the one inflowcell via the partition wall by at least 1.0 mm.

According to a sixth aspect of the present invention, the honeycombfilter according to the fifth aspect is provided, wherein the plugginglength L_(OUT) of the outflow side plugging portion disposed in the oneinflow cell is larger than the plugging length L_(IN) of the inflow sideplugging portion disposed in the outflow cell adjacent to the one inflowcell via the partition wall by 1.0 to 4.0 mm.

According to a seventh aspect of the present invention, the honeycombfilter according to any one of the first to sixth aspects is provided,wherein the outflow cells and the inflow cells have different shapes atopen ends.

According to an eighth aspect of the present invention, the honeycombfilter according to any one of the first to seventh aspects is provided,wherein an area S_(OUT) of the outflow cells at the open ends and anarea S_(IN) of the inflow cells at the open ends are different.

According to a ninth aspect of the present invention, the honeycombfilter according to the eighth aspect is provided, wherein the areaS_(OUT) of the outflow cells at the open ends is larger than the areaS_(IN) of the inflow cells at the open ends.

According to a tenth aspect of the present invention, the honeycombfilter according to any one of the first to ninth aspects is provided,wherein the honeycomb substrate has a cell configuration, in which aplurality of the inflow cells surround one of the outflow cells.

According to an eleventh aspect of the present invention, the honeycombfilter according to any one of the first to tenth aspects is provided,wherein the outflow cells has a quadrangular cell shape and the inflowcells have a pentagonal or hexagonal cell shape.

According to a twelfth aspect of the present invention, the honeycombfilter according to any one of the first to eleventh aspects isprovided, including: a plurality of the honeycomb substrates; and abonding layer disposed between lateral faces of the plurality ofhoneycomb substrates.

The honeycomb filter of the present invention includes a honeycombsubstrate having a partition wall that defines two inflow cells, andtherefore it has the effect of having excellent temperature-risingproperty. The honeycomb filter of the present invention further has aremarkable effect of increasing the deposition limit of particulatematter, such as soot, during the regeneration operation to burn the soottrapped with the honeycomb filter for removal.

The honeycomb filter of the present invention is configured so that theaverage of the plugging length L_(IN) at the inflow side pluggingportion is relatively small. With this configuration, effectivefiltering area of the honeycomb substrate can be obtained favorably, andan increase in pressure loss of the honeycomb substrate can beeffectively suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically showing one embodiment of thehoneycomb filter of the present invention.

FIG. 2 is a plan view schematically showing the inflow end face of thehoneycomb filter of FIG. 1.

FIG. 3 is a plan view schematically showing the outflow end face of thehoneycomb filter of FIG. 1.

FIG. 4 is a schematic cross-sectional view taken along the line X-X′ ofFIG. 2.

FIG. 5 is an enlarged plan view of the range surrounded with the brokenline indicated with P in FIG. 2.

FIG. 6 is a schematic view to explain the method of calculating theaverage of the plugging length in one embodiment of the honeycomb filterof the present invention.

FIG. 7 is a perspective view schematically showing another embodiment ofthe honeycomb filter of the present invention.

FIG. 8 is a plan view schematically showing the inflow end face of thehoneycomb filter of FIG. 7.

FIG. 9 is a perspective view schematically showing one honeycombsubstrate making up the honeycomb filter of FIG. 7.

FIG. 10 is a plan view schematically showing the inflow end face of thehoneycomb substrate of FIG. 9.

FIG. 11 is a schematic cross-sectional view taken along the line Y-Y′ ofFIG. 10.

FIG. 12 is a schematic view to explain the method of calculating theaverage of the plugging length in the another embodiment of thehoneycomb filter of the present invention.

FIG. 13 is an enlarged plan view schematically showing the inflow endface of further another embodiment of the honeycomb filter of thepresent invention.

FIG. 14 is an enlarged plan view schematically showing the inflow endface of further another embodiment of the honeycomb filter of thepresent invention.

FIG. 15 is an enlarged plan view schematically showing the inflow endface of further another embodiment of the honeycomb filter of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following describes embodiments of the present invention. Thepresent invention is not limited to the following embodiments, and is tobe understood to include the following embodiments, to whichmodifications and improvements are added as needed based on the ordinaryknowledge of a person skilled in the art without departing from thescope of the present invention.

(1) Honeycomb Filter:

One embodiment of the honeycomb filter of the present invention is ahoneycomb filter 100 as shown in FIGS. 1 to 5. The honeycomb filter 100includes a honeycomb substrate 4, a plurality of inflow side pluggingportions 5 a and a plurality of outflow side plugging portions 5 b. Thehoneycomb substrate 4 includes a porous partition wall 1. In thehoneycomb substrate 4, a plurality of cells 2 are defined by the porouspartition wall 1, and the plurality of cells extend from the inflow endface 11 to the outflow end face 12 and serve as a through channel offluid. The inflow side plugging portion 5 a is disposed at the inflowend face 11 of the honeycomb substrate 4 to plug the open ends ofoutflow cells 2 b that are a part of the plurality of cells 2. Theoutflow side plugging portion 5 b is disposed at the outflow end face 12of the honeycomb substrate 4 to plug the open ends of inflow cells 2 aother than the outflow cells 2 b of the plurality of cells 2. In thehoneycomb filter 100 of the present embodiment, the honeycomb substrate4 has a partition wall 1 a to define two inflow cells 2 a by division.Hereinafter the partition wall 1 a to define two inflow cells 2 a bydivision may be called a “partition wall 1 a to divide the inflow cells2 a”. The partition wall 1 a to define two inflow cells 2 a by divisionrefers to a partition wall having a certain width or more in thedividing direction in the state of dividing the two inflow cells 2 a.

The honeycomb filter 100 is configured so that the outflow side pluggingportion 5 b disposed in the inflow cells 2 a of the honeycomb substrate4 has the average of the plugging length L_(OUT) that is larger than theaverage of the plugging length L_(IN) of the inflow side pluggingportion 5 a disposed in the outflow cells 2 b of the honeycomb substrate4.

The thus configured honeycomb filter 100 includes the honeycombsubstrate 4 having the partition wall 1 a that defines two inflow cells2 a by division, and so the honeycomb filter can have the effect ofhaving excellent temperature-rising property. The honeycomb filter 100further has a remarkable effect of increasing the deposition limit ofparticulate matter, such as soot, during the regeneration operation toburn the soot trapped with the honeycomb filter 100 for removal. Thatis, the honeycomb filter 100 of the present embodiment is configured sothat the heat capacity is large at the outflow end face 12. With thisconfiguration, if the soot trapped by the honeycomb filter 100 isgradually carried away with the flow of exhaust gas toward the outflowend face 12 of the inflow cells 2 a, cracks at the outflow end face 12can be suppressed effectively during the regeneration operation.

The honeycomb filter 100 is configured so that the average of theplugging length L_(IN) of the inflow side plugging portion 5 a isrelatively small, and therefore the effective filtering area of thehoneycomb substrate 4 can be kept favorably and a rise in pressure lossof the honeycomb substrate 4 can be suppressed effectively.

FIG. 1 is a perspective view schematically showing one embodiment of thehoneycomb filter of the present invention. FIG. 2 is a plan viewschematically showing the inflow end face of the honeycomb filter ofFIG. 1. FIG. 3 is a plan view schematically showing the outflow end faceof the honeycomb filter of FIG. 1. FIG. 4 is a schematic cross-sectionalview taken along the line X-X′ of FIG. 2. FIG. 5 is an enlarged planview of the range surrounded with the broken line indicated with P inFIG. 2. In the descriptions, the inflow side plugging portion and theoutflow side plugging portion may be called collectively a “pluggingportion” simply.

In the honeycomb filter 100, “the average of the plugging length L_(IN)of the inflow side plugging portion 5 a” and “the average of theplugging length L_(OUT) of the outflow side plugging portion 5 b” arevalues obtained as follows. FIG. 6 is a schematic view to explain themethod of calculating the average of a plugging length in one embodimentof the honeycomb filter of the present invention. FIG. 6 is a plan viewshowing the inflow end face 11 of the honeycomb substrate 4 in thehoneycomb filter 100.

To obtain “the average of the plugging length L_(IN) of the inflow sideplugging portion”, one straight line P1 is firstly determined in theinflow end face 11 of the honeycomb substrate 4 as shown in FIG. 6 sothat the straight line passes through the center of the inflow end face11. Next, three straight lines are determined by rotating the straightline P1 clockwise by 45 degrees about the center of the inflow end face11 as the rotation axis. These three straight lines are called straightline P2, straight line P3, and straight line P4. Eight intersections ofthese straight lines P1, P2, P3, and P4 with the circumference of thehoneycomb substrate 4 are set as measuring points a to h. For straightline P1, two points that divide the straight line P1 into 4 equal partson the inflow end face 11 of the honeycomb substrate 4 are set asmeasuring points i and k. For straight line P3, two points that dividethe straight line P3 into 4 equal parts on the inflow end face 11 of thehoneycomb substrate 4 are set as measuring points j and l. The center ofthe inflow end face 11 is set as measuring point m. In this way,thirteen measuring points a to m are determined. When “the average ofthe plugging length L_(IN) of the inflow side plugging portion” isobtained, thirteen outflow cells 2 b (see FIG. 4) located at the closestpositions from the measuring points a to m are found. Then, the lengthsof the inflow side plugging portions 5 a (see FIG. 4) disposed in thesethirteen outflow cells 2 b (see FIG. 4) are obtained. Then, the averageof the lengths of the thirteen inflow side plugging portions 5 a (seeFIG. 4) is found as “the average of the plugging length L_(IN) of theinflow side plugging portion”.

The length of one inflow side plugging portion can be measured asfollows. Firstly, the length of the honeycomb substrate from the inflowend face to the outflow end face is measured. Next, a pin gauge isinserted into the outflow cell having the inflow side plugging portionto be measured from the open end of the outflow end face, and the lengthof the cell is measured at a part without the inflow side pluggingportion. Then, “the length of the cell at a part without the pluggingportion” measured with the pin gauge is subtracted from “the length ofthe honeycomb substrate from the inflow end face to the outflow endface”, whereby the length of the inflow side plugging portion can beobtained. The pin gauge is a rod-like measuring instrument made of adurable material. The pin gauge preferably has a diameter selectedappropriately, depending on the size of the open end of the cell forinserting the pin gauge. For instance, a pin gauge of 0.7 mm in diametercan be used for a quadrangular cell of 0.8 mm in one side. Especially asa pin gauge to measure the length of a cell at a part without the inflowside plugging portion, such a pin gauge preferably has a diameter of 85%or more of the length of one side of the open end of the cell to bemeasured.

When “the average of the plugging length L_(OUT) of the outflow sideplugging portion” is obtained, thirteen inflow cells 2 a (see FIG. 4)located at the closest positions from the measuring points a to m arefound. Then, the lengths of the outflow side plugging portions 5 b (seeFIG. 4) disposed in these thirteen inflow cells 2 a (see FIG. 4) areobtained. Then, the average of the lengths of the thirteen outflow sideplugging portions 5 b (see FIG. 4) is found as “the average of theplugging length L_(OUT) of the outflow side plugging portion”.

Similarly to the length of the inflow side plugging portion, the lengthof one outflow side plugging portion can be obtained by subtracting “thelength of the cell at a part without the plugging portion” measured witha pin gauge from “the length of the honeycomb substrate from the inflowend face to the outflow end face”.

The average of the plugging length L_(OUT) of the outflow side pluggingportion is larger than the average of the plugging length L_(IN) of theinflow side plugging portion at least by 1.0 mm, more preferably by 1.0to 4.0 mm. For instance, even when the average of the plugging lengthL_(OUT) is larger than the average of the plugging length L_(IN), if adifference therebetween is less than 1.0 mm, the effect of suppressingcracks at the outflow end face may not be obtained sufficiently orpressure loss of the honeycomb filter may increase excessively.

The average of the plugging length L_(OUT) of the outflow side pluggingportion is preferably 3.5 mm or more, more preferably 3.5 to 8.5 mm, andparticularly preferably 3.5 to 7.0 mm. If the average of the plugginglength L_(OUT) of the outflow side plugging portions is less than 3.5mm, the outflow side plugging portion may easily fall from the inflowcells. If the average of the plugging length L_(OUT) of the outflow sideplugging portion is too large, the effect of suppressing cracks at theoutflow end face can be obtained, but pressure loss of the honeycombfilter may increase.

In the honeycomb filter of the present embodiment, the length of theplugging portion can be compared among the thirteen measuring points ato m used for obtaining “the average of the plugging length L_(IN) ofthe inflow side plugging portion” and “the average of the plugginglength L_(OUT) of the outflow side plugging portion” as stated above.For instance, the plugging length L_(OUT) of the outflow side pluggingportion disposed in one inflow cell is preferably larger than theplugging length L_(IN) of the inflow side plugging portion disposed inthe outflow cell adjacent to the one inflow cell via the partition wall.Especially, in comparison of the plugging length of the plugging portionbetween one inflow cell and an outflow cell adjacent to the one inflowcell via the partition wall, the following configuration is preferable.That is, the plugging length L_(OUT) of the outflow side pluggingportion is larger than the plugging length L_(IN) of the inflow sideplugging portion at least by 1.0 mm more preferably, and by 1.0 to 3.0mm particularly preferably.

The shape of cells in the plane perpendicular to the extending directionof the cells is not limited especially. Note here that the honeycombsubstrate has a partition wall to divide the inflow cells, and theinflow cells have a part of the shape that is defined by the “partitionwall to divide the inflow cells”. For instance, the cells may have apolygonal shape, such as a triangle, a quadrangle, a hexagon, and anoctagon. The cell shape may be different between the inflow cells andthe outflow cells.

The honeycomb filter 100 shown in FIGS. 1 to 5 are different in shapebetween the open ends of the outflow cells 2 b and the open ends of theinflow cells 2 a. In the honeycomb filter 100, the open ends of theoutflow cells 2 b have a quadrangular shape and the open ends of theinflow cells 2 a have a pentagonal shape. The partition wall 1 a isdisposed to divide these pentagonal inflow cells 2 a. When the honeycombfilter 100 are different in shape at the open ends between the outflowcells 2 b and the inflow cells 2 a, these open ends may have shapesother than a quadrangle and a pentagon as stated above.

For the shape of the open ends of the outflow cells and the inflowcells, a “quadrangle”, for example, includes a quadrangular shape, aquadrangular shape having at least one curved corner of the quadrangle,a quadrangular shape having at least one corner of the quadrangle thatis linearly chamfered, and the like. Similarly, a “pentagon” includes apentagonal shape, a pentagonal shape having at least one curved cornerof the pentagon, a pentagonal shape having at least one corner of thepentagon that is linearly chamfered, and the like. In the following,when the shape of the open ends of the outflow cells and the inflowcells are other polygons, such a polygon includes a polygonal shapehaving at least one curved corner of the polygon, a polygonal shapehaving at least one corner of the polygon that is linearly chamfered,and the like.

In the honeycomb filter 100, the area S_(OUT) of the outflow cells 2 bat the open ends and the area S_(IN) of the inflow cells 2 a at the openends are preferably different. More preferably the area S_(oUT) of theoutflow cells 2 b at the open ends is larger than the area S_(IN) of theinflow cells 2 a at the open ends. This configuration leads to theeffect of decreasing its pressure loss.

The honeycomb substrate 4 of the honeycomb filter 100 has a cellconfiguration such that a plurality of inflow cells 2 a surround anoutflow cell 2 b. Specifically it has a cell configuration such thateight inflow cells 2 a of a pentagonal shape at the open ends surroundone outflow cell 2 b of a quadrangular shape at the open end. With thisconfiguration, the honeycomb filter 100 has a remarkable effect ofsuppressing a rise in pressure loss of the honeycomb filter effectively,and having excellent temperature-rising property of the inflow cells 2 aas well as excellent heat-retaining property of the inflow cells 2 a.

“A plurality of inflow cells 2 a surrounding one outflow cell 2 b”refers to the following configuration in the cross section perpendicularto the extending direction of the cells 2. The following describes theexample where the outflow cells 2 b have a quadrangular shape as shownin FIGS. 1 to 5. Firstly, these cells are disposed so that one side ofeach of the inflow cells 2 a is adjacent to each of the four sides ofthe one outflow cell 2 b. At this time, one side of two or more inflowcells 2 a may be adjacent to one side of the one outflow cell 2 b. Thatis, they may be disposed so that one side of one inflow cell 2 a isadjacent to one side of the one outflow cell 2 b at a half of the oneside, and one side of another inflow cell 2 a is adjacent to the oneside of the one outflow cell 2 b at the remaining half. Then, all of theinflow cells 2 a adjacent to the one outflow cell 2 b are disposed sothat their one sides are adjacent to each other between the adjacentinflow cells 2 a. Such an arrangement of the inflow cells 2 a refers to“a plurality of inflow cells 2 a surrounding one outflow cell 2 b”.

The thickness of the partition wall of the honeycomb substrate ispreferably 0.13 to 0.43 mm, more preferably 0.15 to 0.38 mm, andparticularly preferably 0.20 to 0.33 mm. Too small thickness of thepartition wall may lead to deterioration in mechanical strength of thehoneycomb substrate. Too large thickness of the partition wall may leadto increase in pressure loss of the honeycomb substrate.

The honeycomb substrate preferably has a cell density of 31 to 62cells/cm², more preferably 39 to 55 cells/cm², and particularlypreferably 46.5 to 55 cells/cm². If the cell density is less than 31cells/cm², the mechanical strength of the honeycomb substrate maydeteriorate. If the cell density exceeds 62 cells/cm², the pressure lossof the honeycomb filter may increase, or when the filter is loaded withcatalyst, the cells may be clogged with the loaded catalyst.

The partition wall of the honeycomb substrate preferably has a porosityof 30 to 70%, more preferably 35 to 70%, and particularly preferably 40to 70%. If the porosity of the partition wall is less than 30%, thepressure loss may increase. If the porosity of the partition wallexceeds 70%, the strength of the honeycomb substrate is not enough. Whensuch a honeycomb filter is stored in a can used for an exhaust-gaspurifying apparatus, it is difficult to hold the honeycomb filter with asufficient grip force. The porosity of the partition wall is a valuemeasured with a mercury porosimeter. An example of the mercuryporosimeter includes Autopore 9500 (product name) produced byMicromeritics Co.

From the viewpoint of strength, heat resistance, durability, and thelike, the partition wall is made of various types of ceramics, such asoxides and non-oxides, and metals as major components. Specifically,ceramics include at least one type of materials selected from the groupconsisting of cordierite, mullite, alumina, spinel, silicon carbide,silicon nitride, and aluminum titanate. Examples of the metals includeFe—Cr—Al based metals and metal silicon. One type or two types or moreselected from these materials may be preferably included as a majorcomponent. Particularly preferably, one type or two types or moreselected from the group consisting of alumina, mullite, aluminumtitanate, cordierite, silicon carbide, and silicon nitride is containedas a major component from the viewpoints of high strength and high heatresistance. The ceramic material may be a composite material obtained bybinding silicon carbide particles with cordierite as a binder, forexample. Silicon carbide or silicon-silicon carbide composite materialsare particularly suitable from the viewpoints of high heat conductivityand high heat resistance. Herein, the “major component” refers to thecomponent making up 50 mass % or more of the components, preferably 70mass % or more, and more preferably 80 mass % or more.

The overall shape of the honeycomb filter is not limited especially. Forthe overall shape of the honeycomb filter of the present embodiment, theinflow end face and the outflow end face preferably have a circular formor an elliptic shape, and preferably have a circular form. The size ofthe honeycomb filter is not limited especially, and the length from theinflow end face to the outflow end face is preferably 50 to 305 mm. Whenthe overall shape of the honeycomb filter is a round pillar-shape, theirend faces particularly preferably have a diameter of 25 to 330 mm.

The honeycomb filter of the present embodiment is preferably used as amember for exhaust-gas purification in an internal combustion engine. Inthe honeycomb filter of the present embodiment, at least one of thesurface of the partition wall and the pores of the partition wall of thehoneycomb substrate may be loaded with catalyst for exhaust-gaspurification.

The following describes another embodiment of the honeycomb filter ofthe present invention, with reference to FIGS. 7 to 11. FIG. 7 is aperspective view schematically showing another embodiment of thehoneycomb filter of the present invention. FIG. 8 is a plan viewschematically showing the inflow end face of the honeycomb filter ofFIG. 7. FIG. 9 is a perspective view schematically showing one honeycombsubstrate making up the honeycomb filter of FIG. 7. FIG. 10 is a planview schematically showing the inflow end face of the honeycombsubstrate of FIG. 9. FIG. 11 is a schematic cross-sectional view takenalong the line Y-Y′ of FIG. 10.

The honeycomb filter 200 in FIGS. 7 and 8 includes a plurality ofhoneycomb substrates 24, a plurality of inflow side plugging portions 25a, a plurality of outflow side plugging portions 25 b (see FIG. 11), anda bonding layer 27. That is, the honeycomb filter 200 is asegmented-structured honeycomb filter made up of the collective form ofa plurality of honeycomb substrates 24. The bonding layer 27 is disposedbetween lateral faces of the plurality of honeycomb substrates 24 tobond the plurality of honeycomb substrates 24.

The honeycomb substrate 24 includes a porous partition wall 21. In thehoneycomb substrate 24, a plurality of cells 22 are defined by theporous partition wall 21, and the plurality of cells extend from theinflow end face 31 to the outflow end face 32 and serve as a throughchannel of fluid. The inflow side plugging portion 25 a is disposed atthe inflow end face 31 of the honeycomb substrate 24 to plug the openends of the outflow cells 22 b. The outflow side plugging portion 25 bis disposed at the outflow end face 32 of the honeycomb substrate 24 toplug the open ends of the inflow cells 22 a.

In the honeycomb filter 200, at least one honeycomb substrate 24 isconfigured as in the honeycomb substrate 24 shown in FIGS. 9 to 11. Thatis, the honeycomb substrate 24 of the honeycomb filter 200 has apartition wall 21 a to define two inflow cells 22 a by division. Thatis, similarly to the honeycomb filter 100 shown in FIGS. 1 to 3, thehoneycomb substrate 24 of the honeycomb filter 200 has the partitionwall 21 a to divide the inflow cells 22 a. The shapes of the inflowcells 22 a and the outflow cells 22 b of the honeycomb substrate 24 arepreferably similar to those of the honeycomb filter of one embodiment asdescribed above, e.g., similar to the honeycomb filter 100 shown inFIGS. 1 to 3. The honeycomb substrate 24 having such a partition wall 1a is configured so that the outflow side plugging portion 25 b disposedin the inflow cells 22 a has the average of the plugging length L_(OUT)that is larger than the average of the plugging length L_(IN) of theinflow side plugging portion 25 a disposed in the outflow cells 22 b.The honeycomb filter 200 including the thus configured honeycombsubstrate 24 can have remarkable effects of having excellenttemperature-rising property and capable of increasing the depositionlimit of particulate matters such as soot. Therefore such a honeycombfilter can effectively suppress cracks due to thermal shock during theregeneration operation to burn the soot trapped for removal.

In the segmented-structured honeycomb filter 200, “the average of theplugging length L_(IN) of the inflow side plugging portion 25 a” and“the average of the plugging length L_(OUT) of the outflow side pluggingportion 25 b” are averages of the plugging lengths of one honeycombsubstrate 24. The average of the plugging length of the honeycombsubstrate 24 can be obtained as follows. FIG. 12 is a schematic view toexplain the method of calculating the average of the plugging length inthe another embodiment of the honeycomb filter of the present invention.FIG. 12 is a plan view showing one honeycomb substrate 24 at the inflowend face 31 that is extracted from the plurality of honeycomb substrates24 making up the honeycomb filter 200.

The honeycomb substrate 24 in FIG. 12 has a quadrangular shape at theinflow end face 31. To obtain “the average of the plugging length L_(IN)of the inflow side plugging portion” of such a honeycomb substrate 24,firstly straight line Q1 and straight line Q3 as diagonal lines arevirtually drawn in the quadrangular inflow end face 31. Two straightlines Q2 and Q4 are virtually drawn so as to connect the midpoints ofthe opposed sides of the quadrangle in the quadrangular inflow end face31. Eight intersections of the straight lines Q1, Q2, Q3, and Q4 withthe circumference of the honeycomb substrate 24 are set as measuringpoints a to h. For straight line Q1, two points that divide the straightline Q1 into 4 equal parts on the inflow end face 31 of the honeycombsubstrate 24 are set as measuring points i and k. For straight line Q3,two points that divide the straight line Q3 into 4 equal parts on theinflow end face 31 of the honeycomb substrate 24 are set as measuringpoints j and l. The center of the inflow end face 31 is set as measuringpoint m. In this way, thirteen measuring points a to m are determined.When “the average of the plugging length L_(IN) of the inflow sideplugging portion” is obtained, thirteen outflow cells 22 b (see FIG. 11)located at the closest position from the measuring points a to m arefound. Then, the lengths of the plugging portions of the inflow sideplugging portions 25 a (see FIG. 11) disposed in these thirteen outflowcells 22 b (see FIG. 11) are obtained. Then, the average of the lengthsof the thirteen plugging portions is obtained as “the average of theplugging length L_(IN) of the inflow side plugging portion”.

When “the average of the plugging length L_(OUT) of the outflow sideplugging portion” is obtained, thirteen inflow cells 22 a (see FIG. 11)located at the closest position from the measuring points a to m arefound. Then, the lengths of the plugging portions of the outflow sideplugging portions 25 b (see FIG. 11) disposed in these thirteen inflowcells 22 a (see FIG. 11) are obtained. Then, the average of the lengthsof the thirteen plugging portions is obtained as “the average of theplugging length L_(OUT) of the outflow side plugging portion”.

The length of one inflow side plugging portion and one outflow sideplugging portion can be obtained by subtracting “the length of the cellat a part without the plugging portion” measured with a pin gauge from“the length of the honeycomb substrate from the inflow end face to theoutflow end face”.

In the segmented-structured honeycomb filter, at least one of theplurality of honeycomb substrates may be configured so that the averageof the plugging length L_(OUT) of the outflow side plugging portions islarger than the average of the plugging length L_(IN) of the inflow sideplugging portions. Note here that preferably all of the honeycombsubstrates are configured so that the average of the plugging lengthL_(OUT) of the outflow side plugging portions is larger than the averageof the plugging length L_(IN) of the inflow side plugging portions.

In the segmented-structured honeycomb filter, the value of a differencebetween the average of the plugging length L_(OUT) of the outflow sideplugging portions and the average of the plugging length L_(IN) of theinflow side plugging portions, for example, is preferably similar tothat of the honeycomb filter of the one embodiment described above.

Various conditions of the bonding layer to bond the plurality ofhoneycomb substrates, such as the material and the thickness, are notlimited especially. For instance, the bonding layer may be configuredsimilarly to a bonding layer in a conventionally well-knownsegmented-structured honeycomb filter.

The following describes further another embodiment of the honeycombfilter of the present invention, with reference to FIG. 13. FIG. 13 isan enlarged plan view schematically showing the inflow end face offurther another embodiment of the honeycomb filter of the presentinvention.

A honeycomb filter 300 in FIG. 13 is configured so that the open ends ofthe outflow cells 42 b and the open ends of the inflow cells 42 a aredifferent in shape. Specifically, the honeycomb filter is different fromthe honeycomb filter 100 shown in FIGS. 1 to 5 in the shape of the openends of the inflow cells 42 a. In the honeycomb filter 300, the openends of the outflow cells 42 b have a quadrangular shape and the openends of the inflow cells 42 a have a hexagonal shape.

The honeycomb filter 300 is preferably configured similarly to thehoneycomb filter 100 shown in FIGS. 1 to 5 other than that the shape ofthe open ends of the inflow cells 42 a is different from that of thehoneycomb filter 100. That is, the honeycomb filter 300 includes ahoneycomb substrate 44, a plurality of inflow side plugging portions 45a and a plurality of outflow side plugging portions (not shown). Thehoneycomb substrate 44 includes a porous partition wall 41. In thehoneycomb substrate 44, a plurality of cells 42 are defined by apartition wall 41, and the plurality of cells extend from the inflow endface 51 to the outflow end face (not shown) and serve as a throughchannel of fluid. The inflow side plugging portion 45 a is disposed atthe inflow end face 51 of the honeycomb substrate 44 to plug the openends of the outflow cells 42 b. Although not shown, the outflow sideplugging portion is disposed at the outflow end face of the honeycombsubstrate 44 to plug the open ends of the inflow cells 42 a.

The honeycomb substrate 44 of the honeycomb filter 300 has a partitionwall 41 a to define two inflow cells 42 a by division. This honeycombfilter 300 is configured so that the average of the plugging lengthL_(OUT) of the outflow side plugging portions is larger than the averageof the plugging length L_(IN) of the inflow side plugging portions.

In this honeycomb filter 300 as well, the honeycomb substrate 44 has acell configuration such that a plurality of inflow cells 42 a surroundan outflow cell 42 b. Specifically it has a cell configuration such thatfour inflow cells 42 a of a hexagonal shape at the open ends surroundone outflow cell 42 b of a quadrangular shape at the open end. With thisconfiguration, the honeycomb filter 300 has a remarkable effect ofsuppressing a rise in pressure loss of the honeycomb filter effectively,and of improving the purification performance of the filter.

The following describes further another embodiment of the honeycombfilter of the present invention, with reference to FIG. 14. FIG. 14 isan enlarged plan view schematically showing the inflow end face offurther another embodiment of the honeycomb filter of the presentinvention.

In the honeycomb filter 400 shown in FIG. 14, the open ends of theoutflow cells 62 b and the open ends of the inflow cells 62 a have ahexagonal shape. The honeycomb filter 400 includes a honeycomb substrate64, a plurality of inflow side plugging portions 65 a and a plurality ofoutflow side plugging portions (not shown). The honeycomb substrate 64includes a porous partition wall 61. In the honeycomb substrate 64, aplurality of cells 62 are defined by the partition wall 61, and theplurality of cells extend from the inflow end face 71 to the outflow endface (not shown) and serve as a through channel of fluid. The inflowside plugging portion 65 a is disposed at the inflow end face 71 of thehoneycomb substrate 64 to plug the open ends of the outflow cells 62 b.Although not shown, the outflow side plugging portion is disposed at theoutflow end face of the honeycomb substrate 64 to plug the open ends ofthe inflow cells 62 a.

The honeycomb substrate 64 of the honeycomb filter 400 has a partitionwall 61 a to define two inflow cells 62 a by division. This honeycombfilter 400 is configured so that the average of the plugging lengthL_(OUT) of the outflow side plugging portions is larger than the averageof the plugging length L_(IN) of the inflow side plugging portions.

In this honeycomb filter 400 as well, the honeycomb substrate 64 has acell configuration such that a plurality of inflow cells 62 a surroundan outflow cell 62 b. With this configuration, the honeycomb filter 400has a remarkable effect of suppressing a rise in pressure loss of thehoneycomb filter effectively, and of improving the purificationperformance of the filter.

The following describes further another embodiment of the honeycombfilter of the present invention, with reference to FIG. 15. FIG. 15 isan enlarged plan view schematically showing the inflow end face offurther another embodiment of the honeycomb filter of the presentinvention.

A honeycomb filter 500 in FIG. 15 is configured so that cells 82 of aquadrangular shape at the open ends and cells 82 of an octagonal shapeat the open ends are defined by a partition wall 81. The inflow cells 82a of a quadrangular shape at the open ends and the inflow cells 82 a ofan octagonal shape at the open ends are disposed alternately via thepartition wall 81 so as to surround one outflow cell 82 b of anoctagonal shape at the open end. In comparison between the cells 82 of aquadrangular shape at the open ends and the cells 82 of an octagonalshape at the open ends, the cells 82 of an octagonal shape at the openends have a relatively large size at the open ends.

The honeycomb filter 500 includes a honeycomb substrate 84, a pluralityof inflow side plugging portions 85 a and a plurality of outflow sideplugging portions (not shown). The honeycomb substrate 84 includes theporous partition wall 81. In the honeycomb substrate 84, a plurality ofcells 82 are defined by the partition wall 81, and the plurality ofcells extend from the inflow end face 91 to the outflow end face (notshown) and serve as a through channel of fluid. The inflow side pluggingportion 85 a is disposed at the inflow end face 91 of the honeycombsubstrate 84 to plug the open ends of the outflow cells 82 b. Althoughnot shown, the outflow side plugging portion is disposed at the outflowend face of the honeycomb substrate 84 to plug the open ends of theinflow cells 82 a.

The honeycomb substrate 84 of the honeycomb filter 500 has a partitionwall 81 a to define two inflow cells 82 a by division. That is, thehoneycomb substrate 84 includes the partition wall 81 a dividing “theinflow cells 82 a of a quadrangular shape at the open ends” and “theinflow cells 82 a of an octagonal shape at the open ends”. Thishoneycomb filter 500 is configured so that the average of the plugginglength L_(OUT) of the outflow side plugging portions is larger than theaverage of the plugging length L_(IN) of the inflow side pluggingportions.

(2) Method for Manufacturing Honeycomb Filter:

The following describes a method for manufacturing the honeycomb filterof the present invention.

Firstly a kneaded material having plasticity is prepared to produce ahoneycomb substrate. The kneaded material to produce a honeycombsubstrate can be prepared by adding additives, such as binder, and wateras needed to a material selected as raw material powder from theaforementioned materials suitable for the partition wall.

Next, the thus prepared kneaded material is extruded, thus producing apillar-shaped honeycomb formed body having a partition wall defining aplurality of cells and a circumferential wall disposed at the outermostcircumference. In the extrusion, a die for the extrusion has anextruding face of the kneaded material, and the extruding face of thedie may have a slit thereon in the reversed shape of the honeycombformed body to be formed. The thus obtained honeycomb formed body may bedried by microwaves and hot air, for example.

Next, the open ends of the cells are plugged with a material similar tothe material used for manufacturing of the honeycomb formed body, thusforming a plugging portion. A method for forming the plugging portioncan follow a conventionally-known method for manufacturing a honeycombfilter. Note here that, when the honeycomb filter of the presentinvention is manufactured, the plugging portion is formed so that theaverage of the plugging length L_(OUT) of the outflow side pluggingportions is larger than the average of the plugging length L_(IN) of theinflow side plugging portions. The inflow side plugging portions and theoutflow side plugging portions are formed while selecting the cells tobe plugged so that there exists the partition wall which defines two ofthe inflow cells by division. The following describes one example of themethod for forming a plugging portion.

Firstly, a mask is applied to the inflow end face of the dried honeycombformed body so as to cover the inflow cells. Next the masked end at theinflow end face of the honeycomb formed body is immersed in slurry forplugging to fill the open ends of the outflow cells without the maskwith the slurry for plugging. Next, a mask is applied to the outflow endface of the honeycomb formed body so as to cover the outflow cells. Nextthe masked end at the outflow end face of the honeycomb formed body isimmersed in slurry for plugging to fill the open ends of the inflowcells without the mask with the slurry for plugging. Subsequently, theslurry for plugging placed at the open ends of the outflow cells and theinflow cells is dried, thus forming the plugging portion to plug theopen ends of the cells. The average of the plugging length L_(IN) of theinflow side plugging portion and the average of the plugging lengthL_(OUT) of the outflow side plugging portion can be adjusted bycontrolling the time to immerse the honeycomb formed body in the slurryfor plugging or the depth of the immersion. The viscosity of the slurryfor plugging used may be changed between at the inflow end face and atthe outflow end face. The filling rate of the slurry for plugging intothe cells correlates with the size of the open ends of the cells.Therefore, when a honeycomb filter to be manufactured has differentsizes between the open ends of the outflow cells and the open ends ofthe inflow cells, the plugging length at the plugging portion can beadjusted using such a difference in size of the open ends.

Next, the thus obtained honeycomb formed body is fired, so as to obtaina honeycomb filter. Temperatures and atmosphere for the firing differaccording to the raw material, and those skilled in the art can selectthe temperature and atmosphere for the firing that are the most suitablefor the selected material. The method for manufacturing the honeycombfilter of the present invention is not limited to the method asdescribed above.

EXAMPLES Example 1

80 parts by mass of silicon carbide powder and 20 parts by mass of Sipowder were mixed to obtain the mixture powder. To the mixture powder,binder, a pore former and water were added to have a forming rawmaterial. Next, the forming raw material was kneaded to have a roundpillar-shaped kneaded material.

Next, the kneaded material was extruded using a die for manufacturing ofa honeycomb formed body to have a honeycomb formed body having aquadrangular-prismatic columnar shape as the overall shape. Sixteenhoneycomb formed bodies were manufactured. In the extrusion, a die forthe extrusion, which was for forming a honeycomb substrate having a cellshape as shown in FIGS. 7 to 11, was used.

Next, this honeycomb formed body was dried by a microwave dryer, andthen was dried completely by a hot-air drier, and then both end faces ofthe honeycomb formed body were cut so as to have predetermineddimensions.

Next, a plugging portion was formed to the dried honeycomb formed body.Specifically a mask was firstly applied to the inflow end face of thehoneycomb formed body so as to cover the inflow cells. Subsequently themasked end of the honeycomb formed body was immersed in slurry forplugging to fill the open ends of the outflow cells without the maskwith the slurry for plugging. Subsequently the outflow end face of thehoneycomb formed body also was filled with slurry for plugging at theopen ends of the inflow cells similarly to the above. Subsequently thehoneycomb formed body having the plugging portion formed was furtherdried by a hot-air drier. When filling with slurry for plugging, thefilling depth of the slurry for plugging was adjusted by controlling theviscosity of the slurry for plugging, the amount of binder added to theslurry for plugging, and the size of the holes bored at the mask.

Next the honeycomb formed body having the plugging portion formedtherein was degreased and fired, so as to obtain a honeycomb fired body.Degreasing was performed at 550° C. for 3 hours. Firing was performed at1,450° C. for 2 hours in an argon atmosphere. The honeycomb fired bodyhad a quadrangular-prismatic columnar shape as the overall shape. Thehoneycomb fired body had a square shape at the end faces, and the squarehad the length of 40 mm in one side. This honeycomb fired body was thehoneycomb substrate of the honeycomb filter.

Next, the thus obtained sixteen honeycomb fired bodies were disposed sothat their lateral faces were opposed mutually, and were bonded with abonding material, so as to manufacture a honeycomb bonded member. Thehoneycomb bonded member were manufactured by bonding the sixteenhoneycomb fired bodies in total so that the honeycomb fired bodies weredisposed four in rows and four in columns at the end faces.

Next the circumferential part of the honeycomb bonded member was groundso that the honeycomb bonded member was circular in the cross sectionperpendicular to the extending direction of the cells. Subsequently, anouter coating material including a ceramic raw material was applied tothe outermost circumference of the ground honeycomb bonded member. Theouter coating material was applied while rotating the honeycomb bondedmember.

The honeycomb bonded member with the outer coating material appliedthereto was treated with heat at 600° C., so as to manufacture ahoneycomb filter of Example 1.

The honeycomb filter of Example 1 had a cell configuration as in thehoneycomb filter 200 shown in FIGS. 7 and 8, in which a plurality ofinflow cells 22 a surround one outflow cell 22 b. Among the inflow cells22 a surrounding the outflow cell 22 b, some of the inflow cells aredefined by the partition wall 21 a dividing the inflow cells 22 a. Inthe field of “cell shape” of Table 1, the cell shape of the honeycombfilter of Example 1 was described as “FIG. 8”. In the field of “cellshape” of Table 1, the cell shape of the honeycomb filter of eachExample was described using the number of drawing to be referred to forthe cell shape. For instance, when FIG. 13 is written in the fields of“cell shape” of Tables 1 to 4, the honeycomb filters of these Exampleshave a shape similar to the cell shape of the honeycomb filter 300 inFIG. 13. Note here that as for the number of the drawing written in thefields of “cell shape” of Tables 1 to 4, the cell shape only should bereferred to in the drawing. That is, the drawing should not be referredto for other configurations of the honeycomb filter, for example, aboutthe overall shape of the honeycomb filter in the drawing or as towhether the honeycomb substrate of the honeycomb filter in the drawinghas a monolithic configuration or a segmented structure. The honeycombfilter of Example 1 had porosity of the partition wall that was 65%. Thepartition wall had a thickness of 0.33 mm. The end faces had a diameterof 143.8 mm and the length in the cell extending direction was 152.4 mm.The cell density was 46.5 cells/cm². The porosity of the partition wallis a value measured with a mercury porosimeter.

For the honeycomb substrate making up the thus obtained honeycombfilter, the average of the plugging length L_(IN) of the inflow sideplugging portion and the average of the plugging length L_(OUT) of theoutflow side plugging portion were measured. The plugging length wasobtained as the average of the measurements at the thirteen measuringpoints a to m as shown in FIG. 12. The length of the plugging portion atthe measuring point a to m was obtained by subtracting “the length ofthe cell at a part without the plugging portion” measured with a pingauge from “the length of the honeycomb substrate from the inflow endface to the outflow end face”. Table 1 shows the average of the plugginglength L of the inflow side plugging portion and the average of theplugging length L_(OUT) of the outflow side plugging portion.

The average of the average of the plugging length L_(IN) of the inflowside plugging portion and the average of the plugging length L_(OUT) ofthe outflow side plugging portion also was obtained. That is, thisaverage was the average of the plugging length L_(IN) and of theplugging length L_(OUT). The obtained average is shown in the field of“average of plugging length” in Table 1.

The value obtained by subtracting the average of the plugging lengthL_(IN) of the inflow side plugging portion from the average of theplugging length L_(OUT) of the outflow side plugging portion is shown inthe field of “L_(OUT)(ave.)−L_(IN)(ave.)” in Table 1.

TABLE 1 Average of Average of L_(OUT) plugging length plugging lengthAverage of (ave.) − Evaluations Evaluations L_(IN) of inflow L_(OUT) ofoutflow plugging L_(IN) on soot on pressure side plugging side plugginglength (ave.) Cell deposition loss portion (mm) portion (mm) (mm) (mm)shape limit property Comp. 5.0 5.0 5.0 0.0 FIG. 8 Reference ReferenceEx. 1 Comp. 5.0 5.0 5.0 0.0 — Fail — Ex. 5 Ex. 1 3.0 7.0 5.0 4.0 FIG. 8Excellent Pass Ex. 2 3.5 7.0 5.3 3.5 FIG. 8 Excellent Pass Ex. 3 3.0 6.54.8 3.5 FIG. 8 Excellent Good Ex. 4 3.0 6.0 4.5 3.0 FIG. 8 ExcellentGood Ex. 5 4.0 7.0 5.5 3.0 FIG. 8 Excellent Pass Ex. 6 4.5 7.0 5.8 2.5FIG. 8 Excellent Pass Comp. 6.0 4.0 5.0 −2.0 FIG. 8 Fail Pass Ex. 6Comp. 7.0 3.0 5.0 −4.0 FIG. 8 Fail Pass Ex. 7

For the honeycomb filter of Example 1, the “deposition limit of soot”and the “pressure loss property” were evaluated by the followingmethods. Table 1 shows the result.

(Evaluation on Deposition Limit of Soot)

First using an engine bench equipped with a 2.2-L diesel engine, apredetermined amount of soot was generated under a constant operatingcondition, and the generated soot was deposited on the surface of thepartition wall of the honeycomb filter of each of Examples andComparative Examples. Next, regeneration treatment was performed usingpostinjection to increase the inlet gas temperature of the honeycombfilter. When pressure loss between before and after passing through thehoneycomb filter began to decrease, the postinjection was stopped, andthe engine was switched to an idle state. The predetermined amount ofsoot deposition before regeneration treatment was gradually increased.This operation was repeated until cracks occurred at the honeycombfilter. The amount of soot deposition that caused cracks in thehoneycomb filter was considered as “deposition limit of soot” of thehoneycomb filter. “Deposition limit of soot” of the honeycomb filter wasevaluated in accordance with the following criteria. In Examples 1 to 6and Comparative Examples 5 to 7, Comparative Example 1 was used as theirreference honeycomb filter. In Examples 7 to 9 and Comparative Examples8, 9, Comparative Example 2 was used as their reference honeycombfilter. In Examples 10 to 12 and Comparative Examples 10, 11,Comparative Example 3 was used as their reference honeycomb filter. InExamples 13 to 15 and Comparative Examples 12, 13, Comparative Example 4was used as their reference honeycomb filter.

Evaluation “excellent”: Let that the “deposition limit of soot” of thereference honeycomb filter is set at 100%, when the “deposition limit ofsoot” of a honeycomb filter to be evaluated is 110% or more, it isevaluated as “excellent”.

Evaluation “good”: Let that the “deposition limit of soot” of thereference honeycomb filter is set at 100%, when the “deposition limit ofsoot” of a honeycomb filter to be evaluated is 100% or more and lessthan 110%, it is evaluated as “good”.

Evaluation “fail”: Let that the “deposition limit of soot” of thereference honeycomb filter is set at 100%, when the “deposition limit ofsoot” of a honeycomb filter to be evaluated is less than 100%, it isevaluated as “fail”.

(Evaluations on Pressure Loss Property)

Pressure loss property of the honeycomb filters was evaluated by thefollowing criteria using the value of pressure loss of the honeycombfilter of Comparative Example 1 measured under the same condition as thereference. In Examples 1 to 6 and Comparative Examples 5 to 7,Comparative Example 1 was used as their reference honeycomb filter. InExamples 7 to 9 and Comparative Examples 8, 9, Comparative Example 2 wasused as their reference honeycomb filter. In Examples 10 to 12 andComparative Examples 10, 11, Comparative Example 3 was used as theirreference honeycomb filter. In Examples 13 to 15 and ComparativeExamples 12, 13, Comparative Example 4 was used as their referencehoneycomb filter.

Evaluation “excellent”: Let that the value of pressure loss of thereference honeycomb filter is set at 100%, when the value of pressureloss of a honeycomb filter to be evaluated is 99.5% or less, it isevaluated as “excellent”.

Evaluation “good”: Let that the value of pressure loss of the referencehoneycomb filter is set at 100%, when the value of pressure loss of ahoneycomb filter to be evaluated exceeds 99.5% and is less than 100%, itis evaluated as “good”.

Evaluation “pass”: Let that the value of pressure loss of the referencehoneycomb filter is set at 100%, when the value of pressure loss of ahoneycomb filter to be evaluated exceeds 100% and is 101% or less, it isevaluated as “pass”.

Examples 2 to 15

Honeycomb filters were manufactured similarly to the method of Example 1other than that the average of the plugging length L_(IN) of the inflowside plugging portion and the average of the plugging length L_(OUT) ofthe outflow side plugging portion were changed as shown in Tables 1 to4. For the honeycomb filters of Examples 2 to 15, the “deposition limitof soot” and the “pressure loss property” were evaluated by the methodsimilar to Example 1. Tables 1 to 4 show the result.

Comparative Examples 1 to 4, 6 to 13

Honeycomb filters were manufactured similarly to the method of Example 1other than that the average of the plugging length L_(IN) of the inflowside plugging portion and the average of the plugging length L_(OUT) ofthe outflow side plugging portion were changed as shown in Tables 1 to4. For the honeycomb filters of Comparative Examples 2 to 4, 6 to 13,the “deposition limit of soot” and the “pressure loss property” wereevaluated by the method similar to Example 1. Tables 1 to 4 show theresult.

Comparative Example 5

In Comparative Example 5, sixteen honeycomb segments were prepared,including quadrangular inflow cells and outflow cells, the inflow cellsand the outflow cells being disposed alternately via a partition wall,and these honeycomb segments were bonded at their lateral faces with abonding material, so as to manufacture a honeycomb bonded member. Nextthe circumferential part of the honeycomb bonded member was ground sothat the honeycomb bonded member was circular in the cross sectionperpendicular to the extending direction of the cells. Subsequently, anouter coating material including a ceramic raw material was applied tothe outermost circumference of the ground honeycomb bonded member. Next,the honeycomb bonded member with the outer coating material appliedthereto was treated with heat at 600° C., so as to manufacture ahoneycomb filter of Comparative Example 5. For the honeycomb filters ofComparative Example 5, the “deposition limit of soot” was evaluated bythe method similar to Example 1. Table 1 shows the result.

TABLE 2 Average of Average of L_(OUT) plugging length plugging lengthAverage of (ave.) − Evaluations Evaluations L_(IN) of inflow L_(OUT) ofoutflow plugging L_(IN) on soot on pressure side plugging side plugginglength (ave.) Cell deposition loss portion (mm) portion (mm) (mm) (mm)shape limit property Comp. 5.0 5.0 5.0 0.0 FIG. 13 Reference ReferenceEx. 2 Ex. 7 5.0 7.0 6.0 2.0 FIG. 13 Excellent Pass Ex. 8 3.5 6.0 4.8 2.5FIG. 13 Excellent Good Ex. 9 5.5 7.0 6.3 1.5 FIG. 13 Excellent PassComp. 4.0 3.0 3.5 −1.0 FIG. 13 Fail Excellent Ex. 8 Comp. 7.0 4.0 5.5−3.0 FIG. 13 Fail Pass Ex. 9

TABLE 3 Average of Average of L_(OUT) plugging length plugging lengthAverage of (ave.) − Evaluations Evaluations L_(IN) of inflow L_(OUT) ofoutflow plugging L_(IN) on soot on pressure side plugging side plugginglength (ave.) Cell deposition loss portion (mm) portion (mm) (mm) (mm)shape limit property Comp. 5.0 5.0 5.0 0.0 FIG. 14 Reference ReferenceEx. 3 Ex. 10 4.0 7.0 5.5 3.0 FIG. 14 Excellent Pass Ex. 11 3.0 7.0 5.04.0 FIG. 14 Excellent Pass Ex. 12 3.0 5.5 4.3 2.5 FIG. 14 Good GoodComp. 6.0 3.0 4.5 −3.0 FIG. 14 Fail Good Ex. 10 Comp. 5.0 4.0 4.5 −1.0FIG. 14 Fail Good Ex. 11

TABLE 4 Average of Average of L_(OUT) plugging length plugging lengthAverage of (ave.) − Evaluations Evaluations L_(IN) of inflow L_(OUT) ofoutflow plugging L_(IN) on soot on pressure side plugging side plugginglength (ave.) Cell deposition loss portion (mm) portion (mm) (mm) (mm)shape limit property Comp. 5.0 5.0 5.0 0.0 FIG. 15 Reference ReferenceEx. 4 Ex. 13 6.0 7.0 6.5 1.0 FIG. 15 Excellent Pass Ex. 14 3.5 5.5 4.52.0 FIG. 15 Good Good Ex. 15 4.0 6.0 5.0 2.0 FIG. 15 Excellent PassComp. 5.0 3.0 4.0 −2.0 FIG. 15 Fail Fail Ex. 12 Comp. 7.0 4.0 5.5 −3.0FIG. 15 Fail Pass Ex. 13

(Results)

For the honeycomb filters of Examples 1 to 15, all of the honeycombfilters had the results of “excellent” to “pass” successfully for theevaluations on the “deposition limit of soot” and the “pressure lossproperty”. Particularly the honeycomb filters of Examples 1 to 11, 13,and 15 had particularly excellent results for the evaluations on thedeposition limit of soot.

In comparison between the honeycomb filters of Examples 2 to 7 andComparative Examples 6 and 7, as the sum of the plugging length of theinflow side plugging portion and the plugging length of the outflow sideplugging portion decreased, a better evaluation on the pressure lossproperty was confirmed. As the plugging length of the outflow sideplugging portion increased, a tendency of improving the deposition limitof soot was confirmed. Similar tendency was confirmed also for Examples8, 9 having the cell shape of FIG. 13, Examples 10 to 12 having the cellshape of FIG. 14, and Examples 13 to 15 having the cell shape of FIG.15.

A honeycomb filter of the present invention can be used for a filter topurify exhaust gas.

DESCRIPTION OF REFERENCE NUMERALS

1, 21, 41, 61, 81: partition wall, 1 a, 21 a, 41 a, 61 a, 81 a:partition wall (partition wall that defines two inflow cells bydivision), 2, 22, 42, 62, 82: cell, 2 a, 22 a, 42 a, 62 a, 82 a: inflowcell, 2 b, 22 b, 42 b, 62 b, 82 b: outflow cell, 3, 23: circumferentialwall, 4, 24, 44, 64, 84: honeycomb substrate, 5, 25 b, 45, 65, 85:plugging portion, 5 a, 25 a, 45 a, 65 a, 85 a: inflow side pluggingportion, 5 b, 25 b: outflow side plugging portion, 11, 31, 51, 71, 91:inflow end face, 12, 32: outflow end face, 27: bonding layer, 100, 200,300, 400, 500: honeycomb filter, P1, P2, P3, P4: straight line, Q1, Q2,Q3, Q4: straight line

What is claimed is:
 1. A honeycomb filter comprising: a pillar-shapedhoneycomb substrate including a porous partition wall that defines aplurality of cells extending from an inflow end face to an outflow endface; an inflow side plugging portion disposed at the inflow end face ofthe honeycomb substrate to plug open ends of outflow cells that are apart of the plurality of cells; and an outflow side plugging portiondisposed at the outflow end face of the honeycomb substrate to plug openends of inflow cells other than the outflow cells of the plurality ofcells, wherein the honeycomb substrate includes the partition wall thatdefines two of the inflow cells by division, and an average of plugginglengths L_(OUT) of the outflow side plugging portions disposed in theinflow cells of the honeycomb substrate is larger than an average ofplugging lengths L_(IN) of the inflow side plugging portions disposed inthe outflow cells of the honeycomb substrate by 1.0 to 4.0 mm, and theaverage plugging lengths L_(OUT) is 3.5 to 7.0 mm.
 2. The honeycombfilter according to claim 1, wherein plugging length L_(OUT) in the cellextending direction of the outflow side plugging portion disposed in oneinflow cell of the inflow cells is larger than plugging length L_(IN) inthe cell extending direction of the inflow side plugging portiondisposed in the outflow cell adjacent to the one inflow cell via thepartition wall.
 3. The honeycomb filter according to claim 2, whereinthe plugging length L_(OUT) of the outflow side plugging portiondisposed in the one inflow cell is larger than the plugging lengthL_(IN) of the inflow side plugging portion disposed in the outflow celladjacent to the one inflow cell via the partition wall by at least 1.0mm.
 4. The honeycomb filter according to claim 3, wherein the plugginglength L_(OUT) of the outflow side plugging portion disposed in the oneinflow cell is larger than the plugging length L_(IN) of the inflow sideplugging portion disposed in the outflow cell adjacent to the one inflowcell via the partition wall by 1.0 to 4.0 mm.
 5. The honeycomb filteraccording to claim 1, wherein the outflow cells and the inflow cellshave different shapes at open ends.
 6. The honeycomb filter according toclaim 1, wherein an area S_(OUT) of the outflow cells at the open endsand an area S_(IN) of the inflow cells at the open ends are different.7. The honeycomb filter according to claim 6, wherein the area S_(OUT)of the outflow cells at the open ends is larger than the area S_(IN) ofthe inflow cells at the open ends.
 8. The honeycomb filter according toclaim 1, wherein the honeycomb substrate has a cell configuration, inwhich a plurality of the inflow cells surround one of the outflow cells.9. The honeycomb filter according to claim 1, wherein the outflow cellshas a quadrangular cell shape and the inflow cells have a pentagonal orhexagonal cell shape.
 10. The honeycomb filter according to claim 1,comprising: a plurality of the honeycomb substrates; and a bonding layerdisposed between lateral faces of the plurality of honeycomb substrates.